Locomotion in fishes:
Fishes are vertebrates with an endoskeleton made up of cartilages or bones.
The fishes have a streamlined body where the head and tail are small when compared to the mid-portion of the body. This shape of the body is known as streamlined.
The fishes have a streamlined shape that allows the flow of water around them quickly, reducing friction, thereby moving the fishes in water fast.
The various other characteristics responsible for their movement in water include skeleton which is covered by strong muscles. Fishes swim in water with the help of fins. They have two paired fins and an unpaired fin.
When a fish swims, these muscles make the front part of the body of the fish to curve to one side as shown in the picture, and the tail move in the opposite side and vice versa. It pushes the fish to move forward by causing a sudden and quick movement. The caudal or tail fin helps in changing direction.
These sudden and quick movements occur in a series with the help of the fins of the tail, making the fishes move ahead.
The other fins on the body of the fishes maintain the balance of their body so that they keep the same direction while swimming.
Locomotion in snakes:
The snakes are vertebrates in which the vertebral column (backbone) is very long. They have many thin muscles interconnected to each other, the backbone, ribs, and the skin, even though these muscles are far from each other.
Slithering movement of snakes
Unlike other animals, snakes lack limbs. Instead, their body is covered with hard scales that help them in crawling.
The body of snakes forms loops when it curves. These loops push the snake forward by pressing against the ground. As the snakes have long bodies, they make many loops. Each of these loops pushes the snake forward, making them move very fast but not in a straight line.
The movement of the snake is known as the slithering movement. Most of the snakes can swim in water also.